Improvement in stereoscopes



E. BIERSTADT.

sTEREoscoPE.

N0.174v,893, PatentecMarch 21, 1876.

l IIFA? fTTET:

y/ v i ILFETERS, FHOTO-LITHOGHAPHER. WASHFNGTON. D C4 UNITED STATES PATENT -CEEICE EDWARD BiERsTnDT, 0E JERSEY CITY, NEW JERSEY.

IMPROVEMENT IN STEREOSCOPES.

Specification forming part of Letters Patent No. 174,893, dated March 21, 1876; application filed v November '17, 1875.

To all whom it may concern:

Be it known that I, EDWARD BIERSTADT, of Jersey City, county of Hudson and State of New Jersey, have made a new and useful Improvement in Stereoseopes, of which the following is a specification, reference being had to the accompanying drawings,in which- Figure 1 is a perspective view., showing-how the stereoscope is used. Fig..2 is also a perspective view, the dotted line indicating the adjustment of the focus. Fig. 3 is an end view, showing the stereoscope closed and the flaps folded in.

The stereoscopic pictures or views are bound in book form, with their bottoms to the back of the book, and their faces to the front or upward when the book lies on its back. To the outer edge of the front cover is attached a double Hap, A B. The two parts A and B are stiff, like the cover, while their junctions ward, and lie extended on the inside of the cover and shut into the book as a part of it, as shown in Fig. 3. In the outer leaf B of the flap are set ltwo eyeglasses, c a, about two and a half inches apart from center to center. These glasses are known as prismatic lensesthat is, they are a double-conveX lens, divided transversely, and so set that their thinedges are toward each other. 'The holes through the leaf in which the glasses are set may be a little more than half anpinch square. They are a trifle larger than the holesfand are so placed therein as to make their general outer surfaces as nearly parallel as practicable With the surface of the leaf in which they are set. This causes the general lines of their inner surfaces to incline toward each other, whereby the lines of light are brought into the proper relative positions.

The width of the front coverfand the focal distance of the lenses should be proportioned j so as to suit the average eye when the whole flap is perpendicular to the cover, leaving exceptional eyes to be accommodated by the adjustability of the glasses.

The operation is as follows: To inspect the pictures the book is .held -open in one hand, with the picture to be examined vertical, while all the leaves between the picture and the front cover are laid horizontally, as shown in Fig. 1. With the other hand the glasses are adjusted to the eyes. The double flap not only enables. this to be done easily and perfectly, but also allows the'planes of the glasses and picture to be parallel with each other at all times. v The manner of adjusting is clearly shown in Fig. 2. l

Having thus describedl my invention, what I claim as new, and desire to secure .by Let ters Patent, is-

As a new article of manufacture, a stereoscopic album consisting of a book, theleaves of which are illustrated with stereoscopic pic-` tures, and to one of the covers of which is hinged a iiap made up in two parts, connected together by a tlexible joint, the upper part of the flap carrying two stereoscopic lenses, said flap being adapted to fold closely between the cover and leaves of the book when closed, giving the same the appearance of an ordinary book, substantially as described.

EDWARD BiERsTADT.

Witnesses:

ALFRED BIX,

GEORGE I. DOE. 

